Use of biosurfactants, microorganism-destructors, and plants for eco-friendly bioremediation technologies on oil-contaminated soils

ABSTRACTIn a previous study we demonstrated that Zinnia hybrida ‘Profusion White’ can be effective in the remediation of oil-contaminated soil. However, the rates of removal of total petroleum hydrocarbons (TPH) were greatest in soils containing 9000 mg/kg TPH and less in soils with higher concentrations of TPH. This study was conducted to investigate the effects of basal fertilizer rates and perlite amendments on the growth of zinnia and its remediation capacity in soils with TPH concentrations of 26,000 mg/kg. Methodology: Soils were prepared with or without TPH at an initial concentration of 26,194 mg/kg, and then each of these soils was amended with either a basal fertilizer rate with or without 20% perlite, or twice the basal fertilizer rate with or without 20% perlite. Pots were prepared with the following treatments in these soils: contaminated soil planted with zinnia (planted-contaminated), uncontaminated soil planted with zinnia (planted-uncontaminated), and contaminated soil not planted with zinnia (unplanted-contaminated). Plant growth, soil dehydrogenase activity (DHA), and TPH concentrations were analyzed at 30 and 60 days after sowing. Results: Plant growth in oil-contaminated and uncontaminated soils was superior in pots with twice the basal fertilizer and with perlite. The DHA values in the planted-uncontaminated treatments were significantly lower than those in the planted-contaminated and unplanted-contaminated treatments. However, the effects of basal fertilizer amount and perlite on the DHA values of the soils were small. The TPH concentrations in the planted-contaminated soils were significantly lower than those in the unplanted-contaminated soils after 30 and 60 days. Furthermore, the TPH concentrations in the planted-contaminated soils were lowest in pots with twice the basal fertilizer and with perlite. Conclusions: These results show how phytoremediation of soils with high levels of oil contamination by Z. hybrida ‘Profusion White’ can be practically enhanced by amending the soil with perlite and higher basal fertilizer rates.

Remediation of saline soils contaminated with crude oil using the halophyte Salicornia persica in conjunction with hydrocarbon-degrading bacteria

Utilization of the oil-contaminated soil as a sustainable resource in rural road construction and rehabilitation in oil-producing countries

Objectives/Scope The oil and gas industry spends significant time and money assessing crude oil impacts in soil. Current industry practice involves sending soil samples to an off-site laboratory for the analysis of total petroleum hydrocarbons (TPH) with standard turnaround times of >5 days. A novel handheld infrared device (RemScan™) can be used to measure crude oil contamination in soil in 20 seconds. This disruptive technology is being used to accelerate site closure, cut laboratory analysis costs, and to collect more data points for increased confidence. This paper presents results from an independent validation trial of the infrared device. Methods, Procedures, Process A number of crude oil contaminated soils were collected from several different tropical sites in South-East Asia. Samples were scanned using the infrared device and then sent to an accredited laboratory for analysis of TPH (C10-C36). Site-specific calibration models were loaded into the infrared device which was then used to predict the TPH concentrations of blind validation samples and the results were compared to the laboratory assay data. Results, Observations, Conclusions The results of the study show an excellent correlation between the infrared device and laboratory assay values in terms of both accuracy and repeatability. The occurrence of false positives and negatives is very low using a common remediation criterion. The outcomes of this study show that the handheld infrared device can be confidently used as an infield screening tool for assessing oil contamination in tropical soils. This paves the way for significant time and cost savings for companies that are assessing and remediating crude oil contaminated soils in tropical regions. Novel/Additive Information The concept of taking the "lab to the field" for measuring crude oil contamination in soil, without compromising data quality, is now a possibility using the new handheld infrared device.

Earthworms are an important component of the soil biota and their response to oil pollution needs to be better understood. Laboratory investigations were undertaken to determine the concentrations of crude oil in soil that leads to death of Lumbricus terrestris and Eisenia fetida and to determine the propensity of L. terrestris to move away from contaminated soil. Clemville sandy clay loam was amended to contain maximum oil contents of 1.5 – 2.5% depending on the particular experiment. Additionally, the ability of L. terrestristo survive in bioremediated oil-contaminated soil was evaluated. An oil content of 0.5% was not harmful to survival of earthworms for 7 d but an oil concentration of 1.5% reduced survival to less than 40%. Bioremediated soil containing 1.2% oil did not reduce survival of L. terrestrisduring 10 d. Survival of L. terrestrisin unweathered oil was improved when free movement between contaminated and uncontaminated soil was possible. Casts of earthworms exposed to oil-containing soil contained 0.2% total petroleum hydrocarbons. An allowable regulatory level of 1% oil contamination in soil may not allow for survival of earthworms.

This study evaluates the effects of some organic manures (cow dung manure, poultry manure, fish pond wastewater) and NPK 15:15:15 fertilizer on oil-contaminated soil using Abelmoschus esculentus as a test plant. The research was conducted under controlled conditions at Nnamdi Azikiwe University, Awka, using a randomized complete block design. Soil samples were collected from an oil-contaminated mechanic workshop and treated with various organic and inorganic amendments. Growth parameters, including plant height, stem girth, leaf area, and number of leaves, were assessed over eight weeks. Results indicate that cow dung manure significantly enhanced plant height (100.33% increase), while fish pond wastewater combined with poultry droppings (FP+PD) showed the least increase (14.03%), suggesting a negative synergistic effect. The combination of cow dung and poultry manure (CD+PD) also exhibited a strong positive effect on plant growth. Soil nitrogen levels were highest in FP+PD-treated soils (5.32±1.06), while phosphorus levels were maximized with poultry droppings alone (22.90±5.80). Contaminated soil had the highest potassium levels (54.37±4.38 ppm), likely due to crude oil contamination. Despite amendments, soil pH remained largely unchanged. Leaf production was significantly enhanced by cow dung and fish pond wastewater, with a 100% increase in four weeks, while poultry droppings alone had no effect. Leaf area expansion was highest in the control group (842%), indicating that manure application may not significantly influence light-harvesting capability. Stem girth increased equally (33.33%) across all treatments except in the control (11.11%), with cow dung and fish pond wastewater showing the most rapid impact. Overall, cow dung manure proved to be the most effective treatment for improving soil fertility and enhancing A. esculentus growth in oil-contaminated soil, followed by fish pond wastewater and poultry droppings. These findings highlight the potential of organic amendments in mitigating oil pollution and promoting plant productivity.

Mangrove plants, which inhabit and form sensitive ecosystems in the intertidal zones of tropical and subtropical coastlines, though vulnerable to petroleum pollution, still maintain their growth under oil contamination. To elucidate the molecular response of mangrove plants to crude oil–sediment mixture, seeds of Avicennia marina were planted and grown on 0, 2.5, 5.0, 7.5 and10 % (w/w) oil-contaminated soil. Plant biomass was highly affected from 3.05 ± 0.28 (Control) to 0.50 ± .07 (10 %) and from 3.47 ± 0.12 to 1.88 ± 0.08 in 2 and 4 months old plants respectively. The expression analysis of 11genes belonging to detoxification pathways in the roots and leaves of 2 and 4 month-old plants was evaluated by qRT-PCR. Our results showed changes in expression levels of Fe-SOD, Mn-SOD, CAT, PRX, PPOs, GSTs, and NAP2 whose products are involved in reactive oxygen species (ROS) and xenobiotic detoxification. PPOA showed the highest expression induction of 43 ± 1.15, followed by CAT (12.61 ± 3.25) and PPOB (6.38 ± 1.34) in leaves of 2 months old seedlings grown on 7.5, 10 and 7.5 % oil contaminated soil respectively. PPOA (39.23 ± 2.1), PRX (32.13 ± 1.2) as well as PPOB (26.11 ± 1.3) showed the highest expression induction in leaves of 4 months old plants grown in 2.5 % oil contaminated soil. Our data indicated that PPOA can be a good biomarker candidate gene for long term exposure to oil contamination in A. marina.

Petroleum pollution has become a substantial challenge in soil ecology. The soil bacterial consortia play a major role in the biodegradation of petroleum hydrocarbons. The main objective of this study was to assess changes in bacterial composition and diversity in oil-contaminated dryland soils. The Illumina MiSeq high-throughput sequencing technique was used to study the bacterial diversity and structural change in hyper-arid oil-contaminated soil in the Arava Valley of Israel. The diversity and abundance of soil bacteria declined significantly following oil pollution. The dominant phyla in the petroleum-contaminated soils were Proteobacteria (~33% higher vs. control soil) and Patescibacteria (~2.5% higher vs. control soil), which are oil-associated and hydrocarbon-degrading bacteria. An opposite trend was found for the Actinobacteria (~8%), Chloroflexi (12%), Gemmatimonadetes (3%), and Planctomycetes (2%) phyla, with the lower abundances in contaminated soil vs. control soil. Investigation of long-term contaminated sites revealed significant genus-level taxonomic restructuring in soil bacterial communities. The most evident changes were observed in Mycobacterium, Alkanindiges, and uncultured bacterium-145, which showed marked abundance shifts between spill and control soils across decades. Particularly, hydrocarbon-degrading genera such as Pseudoxanthomonas demonstrated persistent dominance in contaminated sites. While some genera (e.g., Frigoribacterium, Leifsonia) declined over time, others—particularly Nocardioides and Streptomyces—exhibited substantial increases by 2014, suggesting potential ecological succession or adaptive selection. Minor but consistent changes were also detected in stress-tolerant genera like Blastococcus and Quadrisphaera. The effect of oil contamination on species diversity was greater at the 1975 site compared to the 2014 site. These patterns highlight the dynamic response of bacterial communities to chronic contamination, with implications for bioremediation and ecosystem recovery. The study results provide new insights into oil contamination-induced changes in soil bacterial community and may assist in designing appropriate biodegradation strategies to alleviate the impacts of oil contamination in drylands.

Widespread soil contamination with oil and the toxicity of petroleum hydrocarbons to soil biota make it extremely important to study microbial responses to oil stress. Soil metabolites reflect the main metabolic pathways in the soil microbial community. The examination of changes in the soil metabolic profile and metabolic function is essential for a better understanding of the nature of the pollution and restoration of the disturbed soils. The present study aimed to assess the long-term effect of oil on the ecological state of the soil, evaluate quantitative and qualitative differences in metabolite composition between soil contaminated with oil and non-contaminated soil, and reveal biologically active metabolites that are related to oil contamination and can be used for contamination assessment. A long-term field experiment was conducted to examine the effects of various oil concentrations on the biochemical properties and metabolic profile of the soil. Podzolic soil contaminated with oil demonstrated the long-term inhibition of soil biological activity and vegetation. Oil affected the metabolic activity of soil fungi increasing the production of toxic metabolites. A metabolomic approach was employed to determine soil metabolites. The metabolite profile was found to vary greatly between oil-contaminated and non-contaminated soils. Carbohydrates had the largest number of metabolites negatively affected by oil, while the content of organic acids, phenolic compounds, and terpenoids was mainly increased in oil-contaminated soil. The evaluation of the long-term impact of oil on microbial metabolism can make a valuable contribution to the assessment of soil quality and the activity of soil microorganisms being under stress from oil pollution. The results contribute to a further understanding of the role of microorganisms in the ecological functions of contaminated soil, which can be useful in the development of rehabilitation strategies for disturbed sites.

The impact of oil pollution on coastal vulnerable ecosystems has been a major concern especially, in the Persian Gulf area. The current study was carried out to assess to what extent Avicennia marina can tolerate oil contamination and degrade crude oil polycyclic aromatic hydrocarbons (PAHs) from rhizosphere soil. Seeds of A. marina were grown in control and crude oil-contaminated (2.5, 5.0, 7.5, and 10% w/w) soil under ambient greenhouse conditions. Four-month-old plants were collected, measured for their biometry, and assayed for physiological characteristics in relation to degradation of PAHs. A. marina exposed to petroleum responded by allocating proportionally more biomass to root than shoot, activating enzymatic and non-enzymatic antioxidative mechanisms and removing of PAHs, particularly in lower concentrations of crude oil in the soil. The content of total PAHs in A. marina rhizosphere soil, grown on 2.5, 5.0, 7.5 and 10% oil-treated soils were, respectively, 37 ± 0.4, 21.84 ± 0.27, 12.78 ± 0.11 and 14.74 ± 0.03% lower than non-rhizosphere soil. Comparison of PAHs content of rhizospheric and non-rhizospheric soil also indicated that the highest rate of PAH removal was for acenaphthene (74.63 ± 0.78) in control, fluoranthene (71.18 ± 0.56) in 2.5%, and anthracene (69.45 ± 6.33, 55.66 ± 4.38 and 35.97 ± 0.22) in 5.0, 7.5 and 10% oil-contaminated soil and acenaphthene (74.63 ± 0.78) in control. Activities of peroxidase, ascorbate peroxidase, and polyphenol oxidase were more prominent in the roots of plants exposed to increasing concentrations of oil in soil than control plants. Conversely, the activity of superoxide dismutase decreased. These findings render A. marina as a phytoremediation candidate for small scale oil spills and residual oil pollution in coastal marine environments.

Oil leakage is an environmental issue unnoticed in the present time. The problem of oil leakage and oil contamination is main concern for petroleum harvesting countries. Oil contamination in soil creates health issues in the area surrounding it. The nutrients in the soil get reduced significantly due to oil contamination which makes the land not suitable for cultivation. The oil produces hydrocarbons which makes the civil structures weak and out at risk. The most harmful effects of oil contamination are excessive settlement of structures, breakage of underground pipes, etc. In this project, we are trying to study the effects of oil contamination in the soil and also to find a sustainable solution for it. The soil is contaminated in the percentage from 0 to 20% and the tests on index and engineering properties have been conducted to find the effect of engine oil. In order to stabilize the oil contaminated soil, we use silica fumes as a stabilizing agent. The optimum percentage of silica fume is chosen based on the tests of Index and Engineering properties conducted on the soil with silica fumes. The percentage of oil where the soil properties need stabilization is known and the soil is stabilized with the optimum silica fume percentage.

Here we presented the potential phytoremediation of oil contaminated soil using Sea Buckthorn. Sea Buckthorn successfully adapts to adverse conditions of the oil-contaminated soils and provides the high level of cleaning oil-contaminated soils from oil up to 92.7%, on the fourth year of growth. Sea Buckthorn improves microbiological properties of soil: increases the heterotroph microorganisms by 10 4 times, oil destructive microorganisms – by 6×10 2 , nitrogen-fixing microorganisms by 10 times; moreover, it eliminates soil toxicity, increases content of total nitrogen and ammonia. The surface root system of Sea Buckthorn forms well developed root sprouts, that successfully extends to neighboring areas, improves water-air properties, contributes to the rapid formation of dense soil cover, biomass accumulation, formation of humus and provides prolongation of phytoremediation action. Sterility of pollen and content of carotenoid in Sea Buckthorn leaves in the conditions of oil-contamination were within normal range and testifies to the plant tolerance towards oil contamination. Sea Buckthorn improves the physical, chemical and biological properties of soils, reduces oil contamination, protects the oil contaminated soils from erosion. We could recommend this species for the phytoremediation of oil contaminated soil.

Phytoremediation of petroleum-polluted soils: Application of Polygonum aviculare and its root-associated (penetrated) fungal strains for bioremediation of petroleum-polluted soils

This study investigates the impact of crude oil contamination on the fungal community dynamics in the Evrona Nature Reserve, situated in Israel's hyper-arid Arava Valley. The reserve experienced petroleum-hydrocarbon-spill pollution at two neighboring sites in 1975 and 2014. The initial contamination was left untreated, providing a unique opportunity to compare its effects to those of the second contamination event. In 2022, soil samples were collected from both contaminated areas and nearby clean (control) sites, 47 and 7years after the spills. The taxonomic diversity of fungal community and functional guilds, as well as various properties of the soil, were analyzed. We focused on three functional groups within fungal communities: saprotrophs, symbiotrophs, and pathotrophs. The results revealed a significant decrease in number of fungal species in the contaminated samples over time. Consequently, prolonged effect of crude oil-contaminated soils can facilitate the development of a distinct fungal community, which has adapted to the conditions of oil contamination. This study aims to elucidate the dynamics of fungal communities in oil-contaminated soils, contributing to a better understanding of their behavior and adaptation in such environments.

Maintaining the strength stabilisation is a precondition for reusing oil contaminated soil (OCS) in engineering projects. This study investigated the effects of coastal environment, such as temperature, humidity and water, on the strength and deformation of lime-fly ash solidified OCS. Results indicated that (i) The unconfined compressive strength (UCS), shear strength and deformation of OCS improve obvious after treatment, and as solidified for 28 days, the UCS, cohesion and internal friction angle is 1396 kPa, 400 kPa and 37o, respectively. (ii) Water, humidity and temperature can cause some fluctuations on the strength of solidified OCS, but the strength can stabilise at 776, 1230 and 623 kPa, respectively, which can meet the requirements of the Chinese code. Repellency of oil can relieve the affection of water and humidity, and strength tends to increase in the initial cycle. However, as to higher oil contamination, the temperature could change the viscosity of oil. (iii) The excessive increase in solidified materials is not benefit for the soil stability. Therefore, it suggests that the amount of solidified materials should be optimised according to the actual OCS.